1. Field of the Invention
The present invention relates to a disk apparatus, for example, a magnetic disk apparatus in which a storage medium in the form of a disk is rotated and is accessed.
2. Description of the Related Art
Magnetic disk apparatus have found great use as apparatus incorporated in or externally connected to computers. In recent years, magnetic disk apparatus have been incorporated not only in computers in a narrow sense but also in video devices, digital cameras, vehicle navigation devices, etc.
Magnetic disk apparatus are broadly divided into two types: one called a contact stop/start (CSS) type and one called a load/unload type. In CSS-type magnetic disk apparatus, a magnetic head slider on which a magnetic head for accessing a magnetic disk is fixed (the magnetic head and the magnetic head slider hereinafter referred to, for ease of description, as a magnetic head without being discriminated from each other) is left in a state of being placed on the magnetic disk. When the magnetic disk in a CSS-type magnetic disk apparatus is rotated, the magnetic head is floated by an air flow accompanying the rotation to be is slightly spaced apart from the magnetic disk surface. In this state, the magnetic disk is accessed with the magnetic head.
In load/unload-type magnetic disk apparatus, the magnetic head is moved to a position off the outer circumference of the magnetic disk and maintained in a standby state at this position when the magnetic disk stops rotating (which moving is called unloading), and is moved onto the magnetic disk after the magnetic disk has started rotating (which moving is called loading).
The conventional dominating magnetic disk apparatus have been CSS-type magnetic disk apparatus. However, with the increase in the recording density of magnetic disks in recent years, the surface roughness of magnetic disks has become lower to increase the risk of sticking (stiction) fault such that once the magnetic head is brought into contact with the magnetic disk surface, it sticks to the magnetic disk surface.
With a CSS-type magnetic disk apparatus incorporated in a portable appliance such as a notebook computer, there is a problem that high shock resistance is required of the CSS-type device since the portable appliance is frequently carried, and it is disadvantageous to use the CSS-type device under such a condition since the magnetic head contacts the magnetic disk.
Because of these problems, load/unload-type magnetic disk apparatus have been widely adopted in recent years. Load/unload-type magnetic disk apparatus can have higher shock resistance in comparison with CSS-type devices because the magnetic head is in the standby position off the magnetic disk when the magnetic disk apparatus is not operating.
In the case of load/unload-type magnetic disk apparatus, however, a transient operation to load the magnetic head onto the rotating magnetic disk is involved and there is a problem that the magnetic head is liable to contact and damage the magnetic disk during the transient operation.
The magnetic head is constructed so that a surface of the magnetic head opposite from the floating surface on the magnetic disk side is supported on a projection and the magnetic head is tilted on the projection. Japanese Patent Laid-Open No. 11-250429 discloses a technique of forming this projection at a position offset from a center of the magnetic head on the air flow downstream side. If the projection is formed at such a position, the floating surface of the magnetic head can face easily in a direction on the air flow upstream side to obtain a sufficiently large lifting force. Contact between the magnetic head and the magnetic disk is thereby avoided to reduce the occurrence of scratches on the magnetic disk.
The technique disclosed in Japanese Patent Laid-Open No. 11-250429 as a technique for obtaining a sufficiently large lifting force by supporting the magnetic head on a projection formed at a position offset from the center of the magnetic head on the air flow downstream side entails a problem that the attitude of the magnetic head is unstable since the projection supporting the magnetic head is set at a position offset from the center of the magnetic head. For example, the magnetic head is floated on the air flow upstream side to excessively tilt the magnetic head. Thus, there is a possibility of a considerable reduction in the stability with which the magnetic disk is accessed with the magnetic head.